72 Microseasons of the Pacific Northwest

By late August, the cones of Douglas-fir (Pseudotsuga menziesii) — the Pacific Northwest's dominant and most iconic tree — have completed their year-long growth cycle and are releasing seeds. The distinctive cones, recognizable by the three-pointed bracts that protrude between the scales (resembling, in local lore, the hind feet and tail of a mouse hiding inside), turn from green to tan and begin opening as temperatures fluctuate between warm days and cool nights. Each cone contains dozens of small, papery-winged seeds that spiral down from the tree canopy, sometimes traveling a quarter mile on the wind in good conditions. In mast years — which occur every 5–7 years for Douglas-fir — cone production is spectacularly heavy, and the forest floor fills with fallen cones while branches overhead are thick with them. This seed feast drives sharp surges in populations of seed-eating birds and mammals. Red Crossbills (Loxia curvirostra) — nomadic finches that track conifer seed crops across the Pacific Northwest — often appear in large numbers during Douglas-fir mast years, hanging acrobatically from cone-bearing branches. Squirrels cache enormous quantities of seeds and cones. Clark's Nutcrackers, Steller's Jays, and Chestnut-backed Chickadees all increase their activity in maturing conifer stands. The human dimension of cone ripening was critically important in the timber industry for decades — seed collectors (often working the tops of trees by climbing spurs) would harvest cones in late August and September for reforestation programs across the region. Douglas-fir is still the most planted conifer in Pacific Northwest reforestation projects. Hikers in lowland and montane forests from the Willamette Valley to the west Cascades foothills notice the sudden abundance of fresh cones underfoot, the sound of seeds spiraling in the breeze, and the stepped-up activity of squirrels and seed-eating birds — together composing one of the quiet but pervasive signals that summer's full productivity is concluding.